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Topic Review (Newest First)

11-07-2008 03:10 PM

machine shop tom

Kinda hard to wear the chain since it doesn't have one..........

I'd be willing to bet there are at least a couple of cracked pistons.

A good rebuild (bore, hone, GOOD valve job) with maybe a computer-compatible cam would probably be the best bang for the buck.

Funny how it ran like a top with 6 burnt valves.

tom

11-07-2008 01:26 PM

ap72

The whole thing needs an overhaul, not just the timing set... thoush in these engines there's a little less wear than in others, especially on things like the chain

11-07-2008 01:13 PM

Koolaid

So...... is no one going to call red65 on the comment of putting a new timing chain in it?

11-07-2008 01:08 PM

matt167

I know.. but 29" is closer to 33" than 27" that was my point.. but I would agree, a taller gear would be a great benefit

the other thing to consider, is the flotation tires take more force to turn than a normal tire.

11-07-2008 12:03 PM

red65mustang

matt,
point was size does make a big difference....

stock 29" tire, 70mph=2800 with 3.50 gears...
33" tire is only 2400rpms=70mph with 3.50
33" with 4.11, 70mph=2800 to get back to "stock" acceleration and have more timing....
33" with 4.56 would be more "pep" and quicker wind up in all gears....

F150's have 235 75 15 and are 29" tall.. a 215 75 15 is 27" tall and stock on older rangers

11-07-2008 08:37 AM

red65mustang

the much shorter height oem tires (27"?) are a just barely ok acceleration force match to the stock 3.50 gears...
the 33" tall tires reduces that 3.50 ratio torque multiplication factor to something around 3.00 or less...
plus they work as a lot of added rotational resistance against the motor due to they are heavy....

simple first demo for what a rear gear change does:
reverse gear is just a bit lower ratio than first gear...
floor the truck in reverse and see how quick it gets to the 4400rpms HP peak...versus how long in the taller first gear to reach 4400...
simple demo for the tires diameter and weight, borrow some 24" tall 60 series tires/wheels and test drive...

if you want to mess around for not many bucks and do something that does give results that you will likely feel (atleast a little bit):
replace the timing chain (it's shot!) and put a decent quality rebuilt dist in it (it's shot) and play with the timing curve to better match the wrong gears/tires combo....
you can gain (back) 10HP/20TQ+ over the "whole" rpm range because the spark is delivered when it's supposed to be to make max "power" cylinder pressure ATDC ...
you can add another 10HP/20TQ by tweeking the timing based on the "sweet spot" your motor wants to live at....
factory base timing is a compromise setting, so the car can work anywhere in the world (climate/altitude/etc), almost every motor made responds to from 2* up to 4* more base timing to make more Hg sooner......

my honest opinion, just adding headers to your HEAVY truck and BIG tires will make next to no performance change you can actually feel....
check the cam and heads spec's for the specific motor you are taking the headers off first,,,
if it's not a exact match to your cam and heads those tube headers may well cost you more TQ acceleration force than the added HP is worth....
truck motors are a purpose built design to make the max TQ per rpms possible to accelerate a heavy weight.....
by very carefully controlling the air flow velocity for best possible cylinder fill and A/F mix "atomization" quality when the piston speed is too slow, at less than the TQ peak rpms.....
the stock exhaust and cam and heads set up is part of the total flow equation....

footnote:
LOL! I am so so so happy my son is done with 4X4 trucks!!!
here's his last toy....

11-06-2008 12:02 PM

fordboy08

ok. i would prolly get them from a bone yard this isnt something i put alot of money into its just a play around truck. i havnt really messed around with the manifolds on sixes but when i go to split the intake and exhaust manifolds will i have any problems? right now its got maniflolds from a non smogger motor on it

11-06-2008 11:57 AM

matt167

EFI manifolds are 3/3 split.. and very good flowing

11-06-2008 11:48 AM

Koolaid

I had a 95 with an efi 300 - it had a tubular style header from the factory (I can't remember if it was a 3/3 split style or a single 6 into 1 style). I would have to believe that would be an upgrade over the old log style if you can pick one up cheap at the junkyard.

11-06-2008 11:46 AM

fordboy08

ok well point well taken, its got 3.50 gears in it with np435 running 33x12.50 mud terrain tires and a solid axle conversion up front from a 79' bronco, i realize its an tired motor, and by no means want to push alot of power out of it, but in a previous forum i had heard mention of somebody using exhaust manifolds off a fueley six is there anything special about these manifolds?

11-06-2008 10:41 AM

Koolaid

I haven't personally done this so take it for what it's worth:

I've always heard that a 300 responds well to a small (500cfm) Holley vacuum secondary with the split headers and a small RV style cam. More people might make a 4 barrel intake, but Offenhauser was the only one I've personally seen.

I would go with the others though - 325,000 is a lot of mileage on any engine (even the 300) - I wouldn't try to make a lot of horsepower with it and I wouldn't throw more gear at the thing. It seems like those 300's had the same acceleration if you were unloaded or had 2000lbs in the bed, but they just keep chugging along.

I also agree it is probably better to leave this engine alone, its an old man now!

You could always find a second engine somewhere and build it up in your garage then pop it in when you're ready.

11-06-2008 10:20 AM

red65mustang

leave the motor alone...
swap to lower gears and/or smaller diameter tires....
your fighting a heavy vehicle weight with a likely tired/worn motor....
the deeper gears multiples the flywheel TQ which means less load on the motor accelerating the truck weight so it will last longer...
300ft/lbs x 2.46 first gear x 3.25 rear gears=2400ft/lbs on the tires...
300 x 2.46 x 4.10 rear gears=3,000ft/lbs on the tires
my $.02
you will spend $2000 on the motor for what a $600 gear change will do because of the weight...
when it's worn to the point that oil consumption is a problem,,,then address modifying or better, changing to a bigger motor,,,there's only so much a 300 cube can do....

strip every last pound off the truck you can...

11-06-2008 08:31 AM

killerformula

Even with a new set of gaskets, your bores are probably a bit egg-shaped by now and I'm sure it has some blow-by. It may run forever, but I wouldn't stress the thing out.

Exhaust may get you a little more power, chances are you won't notice it though. Stock exhaust tends to be of higher quality than much of the aftermarket stuff, so you'll probably be taking off a lifetime system to put on one that may last a couple of years.

Just run it, 300's were really never meant to be a performance motor.

K

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